Radar detectors for automotive vehicles have generally comprised three or four typical kinds of assembly. Very often, the radar detector comprises a horn antenna within the same body as the signal handling and alarm circuits, for mounting permanently into a vehicle such as by attachment to the bezel over the windshield, or perhaps by mounting onto the dashboard of the vehicle. Such radar detectors are the sort that have been marketed by a number of manufacturers under such names as FUZZBUSTER (TM), ESCORT (TM), and by the assignee of the present invention as its MICRO EYE (TM) Model 834. In any event, the bulkiness of the radar detector may be a hindrance to vision, or it may be otherwise undesirable from an esthetic point of view--particularly in luxury automobiles.
Thus, manufacturers including paticularly the Assignee of the present invention have provided remote models, where the antenna is mounted within the engine compartment of the vehicle, for example, with an annunciator mounted within the vehicle. An example of such structure is that which is manufactured and sold by the Assignee of the present invention as its MICRO EYE (TM) Model 837.
Neither of the above styles of radar detector assembly have in any way been portable from vehicle to vehicle, such as by an individual who owns more than one automobile, or a truck operator or driver who may wish to utilize his own radar detector in whatever vehicle he may be driving at the time.
A third kind of general assembly has therefore been provided, which has to a great extent been reasonably portable, and that is the kind that has been marketed by the Assignee of the present invention in association with its trade mark HOTSHOT, or as its SELECTRA (TM) Model 841. However, each of those models relied upon its mounting within an automotive vehicle for maximum sensitivity. Since each is generally intended for attachment to a windshield visor, the sensitivity is greatest when the visor is placed in a substantially vertical position for exposure of the radar detector to microwave frequency signals entering the vehicle from the front or the rear of the vehicle, through the vehicle glass and into the passenger compartment thereof. That, however, may again result in decreased visibility in certain circumstances.
The general assembly of radar detectors as spoken of immediately above has been such, however, that those radar detectors employed a microstrip antenna, and thus were relatively flat or thin in a front-to-back dimension. Because those radar detectors did not employ a horn antenna, their physical size could be made smaller; and they functioned with their circuits being substantially mounted vertically--in the same plan as the micro strip antenna--rather than being mounted horizontally behind a horn whose mouth was mounted vertically. Those microstrip radar detectors are, as noted, more portable from vehicle to vehicle, but may work with somewhat less sensitivity unless they can be substantially mounted vertically, and perpendicular to the longitudinal axis of the vehicle, for maximum exposure to horizontally directed microwave frequency radar transmissions.
The general frequencies at which mircowave radar transmissions occur, especially from police radar, are at the X-band (10.525 GHz) and K-band (24.150 GHz). Transmissions at those frequencies will pass through certain kinds of materials that are substantially transparent to them, such as glass and most plastics, but not other kinds of materials--especially metal or metallized surfaces. That is, microwave frequency transmissions will pass through the glass of an automotive vehicle, such as the windshield and side windows, such transmissions will pass through many plastics materials such as those that the cases may be molded from; but they will not pass through the metal of which the vehicle is constructed, neither will they pass through a metallized surface such as the silvering that is provided for rearview mirrors within the vehicle.
It is those latter characteristics that are particularly taken advantage of by the present invention; but moreover, the present invention has achieved one further desideratum that has been demanded by the marketplace and which is accommodated hereby, and that is for a portable radar detector that may be moved from one vehicle to another and that has maximum exposure and thereby maximum sensitivity to radar transmissions, while at the same time being both esthetically mounted within the vehicle and mounted in such a manner as to substantially not increase any vision obstruction particularly for the driver of the vehicle.
The inventor has discovered that, if a radar detector assembly is provided that substantially duplicates the rearview mirror that is always mounted in a vehicle, but at the same time the construction of the radar assembly is such that a microstrip antenna installed within the body of the radar detector is mounted so as to be neither forward nor rearward of either the mirror on the radar detector assembly or the mirror that is permanently installed within the vehicle, so as thereby to be not shielded by either mirror. Because of the mounting position of the vehicle mirror within the vehicle, usually at least somewhat below the top of the vehicle windshield, there is substantially unobstructed exposure of the radar detector assembly at least to radar transmissions entering the vehicle from the front thereof; and in most instances, also to radar transmissions that enter the vehicle from the rear thereof. [It is recognized that, for the most part, meaningful detection and alarm conditions upon exposure to police radar occur when the police radar is physically located either forward of the vehicle--i.e., down the road--or rearward of the vehicle--as in a following police vehicle equipped with a radar transmitter.]
It is also, of course, recognized that the permanently installed mirror in an automotive vehicle is substantially mounted vertically--that is, with its major plane vertical. Thus, by providing a radar detector construction and assembly such that the body of the radar detector may be detachably attached to the mirror that is permanently installed within the vehicle, and that has a mirror on its front face--i.e., facing the rear of the vehicle, the rear face of the radar detector assembly facing the front of the vehicle--then the previous rear view function continues to be served, while at the same time exposing the assembly to radar transmissions. Morever, the structure of the radar detector of the present invention can be modified so that the microstrip antenna may be mounted substantially vertically and substantially perpendicular to the longitudinal axis of the vehicle, while at the same time the mirror on the radar detector may be adjusted so as to provide the maximum and best visibility to any driver in the vehicle, without otherwise affecting or adjusting the vertical and perpendicular mounting of the microstrip antenna to the road surface and to the direction of travel of the vehicle, respectively.
It has always been a problem, however, that area of intruder radar devices that may be installed in buildings for protection and security of those buildings also work at the X and K band frequencies, so that they may also be detected by a radar detector and give a false alarm. Very sophisticated signal handling circuits have been developed by the Assignee of the present invention to discriminate against noise, and need not be discussed herein; but nonetheless especially with radar detectors that are equipped with a microstrip antenna, it is desirable that spurious microwave energy should be shielded against. More particularly, it is very desirable that energy at the intermediate frequency or frequencies of the signal handling circuits should be shielded against--those frequencies being in the 700 MHz to 5.0 GHz range, are also sufficiently high that they may intrude into the passenger compartment of an automotive vehicle--and the present invention provides such shielding by taking advantage of the substantial opaqueness of the vehicle mirror and the mirror which covers a substantial portion of the front face of the radar detector assembly, to both microwave and intermediate frequency transmissions. Thus, the construction of radar detector assemblies according to the present invention provides for the unobstructed exposure of the microstrip antenna to microwave radar frequency transmissions, and for substantially effective shielding of the radar detector signal handling circuits to both microwave and intermediate frequency signals, thereby so as to substantially reduce if not eliminate spurious alarm conditions due to the intrusion of microwave or intermediate frequency signals into the signal handling circuits of the radar detector.